1. Field of the Invention
This invention relates to navigation systems. In one of its aspects, the invention relates to a navigation system in which compass headings are continuously integrated with distance traveled by a water, air or land vehicle to give coordinate position output readings for the vehicle. In another of its aspects, the invention relates to a method for continuously determining position coordinates of a water, air or land vehicle with respect to known positions.
2. State of the Prior Art
It is desirbale and necessary to accurately determine the coordinate position of water and other types of craft. Systems of coordinate plotting by manual calculations are complicated and time consuming. It is desirable to obtain an instantaneous reading of position with respect to fixed known coordinates.
Many compass systems have been developed for maintaining craft on predetermined courses. For example, see U.S. Pat. Nos. to Fowler, 3,772,503, Chance, 2,102,511, and 2,463,245, Best, 2,370,000, Hill, 1,885,098, Helmer, 1,834,399, Smola, 2,063,765 and 2,204,553, and Schulte, 2,518,258. Many of these devices use photocells to detect deviation from a desired heading. The Fowler patent, 3,772,503, discloses a compass card coated with magnetic or light transmissive and opaque segments. The coated information is detected by sensors to produce a digital signal representative of the compass card position with respect to the housing.
Another compass system in which an output heading signal is produced is disclosed in the U.S. Pat. No. to Barbieri et al., 3,480,788. In this system a compass with a photopotentiometer has an output signal representative of the compass heading.
A course plotter for a boat is disclosed in the U.S. Pat. No. to Gray, 3,141,725. In the Gray system a signal representative of a compass heading is integrated with a signal representative of the velocity of the vehicle. The integrated signal is resolved into north-south and east-west components and plotted on a chart.
The Gray system is fairly expensive in that it requires expensive and complicated heading detectors and gear train equipment. Further, the system has inherent compass drag due to the compass drive potentiometer system. Further, the Gray system is difficult to calibrate for magnetic deviation due to the craft in which it is mounted.